Method and device for controlling fuel injection in the bi-fuel internal combustion engine

Abstract

A bi-fuel internal combustion engine is intended for suppressing consumption of gasoline fuel and reducing exhaust emissions; under ordinary operations, a CNG fuel emitting smaller amounts of NOx, HC, CO, and the like as compared with a gasoline fuel, is used as a supply fuel to reduce the exhaust emissions; in this case, a fuel injection device is required for each of the two types of fuel, that is, the gasoline fuel and the CNG fuel and the problem is torque change and fluctuation occurring when the fuel is switched from gasoline to CNG, or vice versa. Control is provided for correcting a fuel injection quantity, an intake air quantity, and ignition timing when the type of fuel supplied to the engine is switched from one type to another. A single fuel injector is used as both an injector of gasiform fuel and an injector of liquid fuel.

What is claimed is:  
     
         1 . A method for controlling fuel injection in a bi-fuel internal combustion engine operating on at least one of a gasiform fuel and a liquid fuel, comprising the step of: 
 providing control of correcting a fuel injection quantity, an intake air quantity, or ignition timing when operation of said bi-fuel internal combustion engine is switched from the operation on said liquid fuel to that on said gasiform fuel, or vice versa.    
     
     
         2 . The method for controlling fuel injection in a bi-fuel internal combustion engine according to  claim 1 , wherein a combined control of correcting the fuel injection quantity and the intake air quantity is provided when the operation of said bi-fuel internal combustion engine is switched from the operation on said liquid fuel to that on said gasiform fuel, or vice versa.  
     
     
         3 . The method for controlling fuel injection in a bi-fuel internal combustion engine according to  claim 1 , wherein a combined control of correcting the fuel injection quantity, the intake air quantity, and the ignition timing is provided when the operation of said bi-fuel internal combustion engine is switched from the operation on said liquid fuel to that on said gasiform fuel, or vice versa.  
     
     
         4 . A device for controlling fuel injection in a bi-fuel internal combustion engine, wherein a fuel injector is used commonly for injecting a gasiform fuel and a liquid fuel.  
     
     
         5 . The device for controlling fuel injection in a bi-fuel internal combustion engine according to  claim 4 , wherein supply of the gasiform fuel or the liquid fuel is selected in accordance with an engine operating condition.  
     
     
         6 . The device for controlling fuel injection in a bi-fuel internal combustion engine according to  claim 4 , wherein an injector dedicated to injection of the gasiform fuel is added to said common injector injecting both gasiform fuel and liquid fuel.  
     
     
         7 . A device for controlling fuel injection in a bi-fuel internal combustion engine, said device being provided with a first fuel injector injecting a liquid fuel and a second fuel injector injecting a gasiform fuel, 
 wherein said liquid fuel injected from said first fuel injector is used for performing a cleaning injection for cleaning said injector dedicated to injection of the gasiform fuel.    
     
     
         8 . The device for controlling fuel injection in a bi-fuel internal combustion engine according to  claim 7 , 
 wherein timing for performing said cleaning injection for cleaning with said liquid fuel said injector dedicated to injection of the gasiform fuel is set to a time of starting or a range at which a throttle valve fully opens.